WO2006069853A1

WO2006069853A1 - Method for the operation of an internal combustion engine

Info

Publication number: WO2006069853A1
Application number: PCT/EP2005/056092
Authority: WO
Inventors: Ernst Wild
Original assignee: Robert Bosch Gmbh
Priority date: 2004-12-23
Filing date: 2005-11-21
Publication date: 2006-07-06
Also published as: CN101087939B; DE102004062018A1; DE102004062018B4; RU2387859C2; US7415345B2; RU2007128087A; JP4683573B2; BRPI0519711A2; US20070168105A1; CN101087939A; JP2008525696A

Abstract

According to the invention, an air level (rl) in a combustion chamber is determined taking into account a pressure (ps) prevailing in a suction duct during operation of an internal combustion engine. Said air level (rl) is determined based on a model (A) which is fed a rotational speed (nmot) of a crankshaft and a ratio between the pressure (ps) prevailing in the suction duct (22) and an ambient pressure (pu) as input variables.

Description

Method for operating an internal combustion engine

State of the art

The invention relates to a method for operating an internal combustion engine, in which an air charge in a combustion chamber is determined taking into account a pressure in an intake passage. The invention further relates to a computer program, an electrical storage medium for a control and / or regulating device of an internal combustion engine, as well as a control and / or regulating device of an internal combustion engine.

A method of the type mentioned is known from the market. In many internal combustion engines, the pressure in an intake passage is measured by means of a pressure sensor. Via a linear relationship, an air charge in the combustion chambers of the internal combustion engine is calculated from the measured pressure. The knowledge of this air filling is important, especially in air-guided systems for the correct metering of the fuel into the combustion chambers of the internal combustion engine. Correct metering of the fuel in turn has an effect on the fuel consumption and the emission behavior of the internal combustion engine. In general, reference is made in this context to DE 197 56 919 A1. Also known are four-stroke internal combustion engines with camshaft overlap. In such

Internal combustion engines can in the region of top dead center between Ausschiebetakt and intake stroke, the exhaust valves and intake valves of a combustion chamber for a certain

Crankshaft area to be open at the same time. As a result, an internal exhaust gas recirculation can be realized by which, inter alia, a reduction of the nitrogen oxide emissions can be achieved. However, it has been found that in such systems with large

Camshaft overlap the determination of the air charge in the combustion chamber so far either complex or inaccurate.

The present invention therefore has the object, a method of the type mentioned in such a way that even in systems with large

Camshaft overlap the most accurate determination of the air charge on the basis of the pressure prevailing in the intake passage is possible.

This object is achieved in a method of the type mentioned fact that the air charge is determined based on a model which receives as input variables, a speed of a crankshaft and a ratio of the pressure in the intake duct to an ambient pressure. In a computer program, an electrical storage medium and a control and / or regulating device of an internal combustion engine, the stated object is achieved accordingly.

Advantages of the invention

According to the invention it has been recognized that in systems with large camshaft overlap a non-linear relationship between existing in a combustion chamber air filling and consists of the pressure prevailing in the intake air pressure. Furthermore, it has been recognized that this non-linear relationship is essentially a function of the ratio between the air pressure prevailing in the intake passage and the ambient pressure. In the method according to the invention, therefore, this ratio is additionally used for determining the air charge present in the combustion chamber. This can therefore be determined in systems with large camshaft overlap with high precision, which in turn, especially when the

Internal combustion engine operates air-controlled, a precise adjustment of a desired fuel-air mixture in the combustion chamber allowed. Ultimately, both the fuel consumption and the emission behavior of the internal combustion engine are improved by the inventive measures.

An advantageous development of the method according to the invention is characterized in that the model additionally receives a temperature of the air present in the combustion chamber as an input variable. As a result, errors due to a change in air density are prevented or at least reduced, and the precision in determining the air charge is further improved.

In a further development, it can be assumed that the temperature of the air present in the combustion chamber is equal to a detected temperature of the air in the intake channel. As a result, the computational effort is reduced, without the precision in determining the air charge is significantly deteriorated.

Alternatively, the temperature of the air present in the combustion chamber can also be determined on the basis of a model which includes a detected temperature as input variables the air in the intake passage and at least one further detected temperature of the internal combustion engine, in particular a cooling water temperature, an exhaust gas temperature and / or a cylinder head temperature receives. This process variant increases precision without the need for additional sensors.

It is also possible that the ambient pressure is determined based on the difference between a detected and a modeled pressure in the intake duct. In this way, a separate sensor for detecting the ambient pressure can be omitted, which saves costs.

In this case, the precision in determining the ambient pressure is increased by the fact that the determination is carried out only when the throttle opening or an equivalent size reaches and / or exceeds a limit value. This is based on the knowledge that the ambient pressure only changes very slowly, so that a continuous determination is not necessary. However, when the throttle valve is comparatively wide or fully opened, the ambient pressure can be determined by integration over the above-mentioned difference with comparatively high precision.

In a further development for this purpose, the modeled pressure in the intake duct can again be determined on the basis of a model which receives as input a difference between an air mass flowing into the intake duct and an air mass flowing from the intake duct into the combustion chamber. By means of this simple mass balance, the pressure in the intake duct can be modeled very simply and likewise with high precision, so that a corresponding pressure sensor can optionally be dispensed with. In this case, in turn, the air mass flowing out of the intake duct into the combustion chamber can be determined on the basis of a model which receives a position of a throttle valve as an input variable. The position of the throttle valve is detected anyway with conventional regulated throttle, so that no additional costs arise.

1. In order to account for manufacturing tolerances and / or signs of wear on the throttle during the determination of the air mass flowing into the combustion chamber, it is advantageous if the corresponding model additionally receives a correction variable of a throttle characteristic which is the difference between modeled and detected pressure in the intake passage is determined. This also serves to increase the precision in determining the reaching into the combustion chamber air mass. In this case, the correction variable is advantageously only determined if the throttle opening or an equivalent size is smaller than a limit value and / or reaches it.

With particularly little storage space, a minimum of sensor effort and little computing time, the abovementioned methods can be realized if at least one of the models comprises a characteristic curve and / or a characteristic diagram.

drawings

Hereinafter, a particularly preferred embodiment of the present invention will be explained in more detail with reference to the accompanying drawings. In the drawing show: Figure 1 is a schematic representation of an internal combustion engine;

FIG. 2 shows a flow chart of a method for determining an air charge;

Figure 3 is a flowchart of a method for determining an ambient pressure and an offset of a throttle characteristic;

FIG. 4 is a flowchart of a method for determining a modeled pressure in an intake passage of the internal combustion engine of FIG. 1;

FIG. 5 shows a flowchart of a method for determining an air mass flowing from the intake duct into the combustion chamber; and

FIG. 6 is a flow chart illustrating the interaction of the methods shown in FIGS. 2-5.

Description of the embodiments

An internal combustion engine carries in FIG. 1 in total

It comprises a plurality of cylinders, of which only one is shown by the reference numeral 12 for reasons of clarity in Figure 1. The corresponding combustion chamber bears the reference numeral 14. Fuel is injected into the combustion chamber 14 directly by means of a fuel injector 16, which is connected to a fuel system 18. Air enters the combustion chamber 14 via an inlet valve 20 and an intake passage 22, in which a throttle valve 24 is arranged. This is adjusted by a servomotor 26, their current position is from a throttle valve sensor 28 detected. The pressure prevailing in the intake passage 22 air pressure is detected by a pressure sensor 30, the corresponding temperature of a combined with this temperature sensor 32. The pressure sensor 30 is located downstream of the throttle valve 24 and measures the pressure in front of the intake valve 20. As will be explained below, when the intake valve 20 closes, pressure equality between the intake passage 22 and the combustion chamber 14 prevails Pressure in the intake passage 22, the air charge in the combustion chamber 14 are determined.

An existing in the combustion chamber 14 fuel-air mixture is ignited by a spark plug 34 which is connected to an ignition system 36. Hot combustion exhaust gases are discharged from the combustion chamber 14 via an exhaust valve 38 and an exhaust pipe 40.

The internal combustion engine 10 shown in Figure 1 is installed in a motor vehicle, not shown. One

Desired by the driver of the motor vehicle is expressed by the position of the accelerator pedal 42. The rotational speed of a crankshaft 44 of the internal combustion engine 10 is tapped off by a rotational speed sensor 46. The operation of the internal combustion engine 10 is controlled by a control and

Control device 48 controlled or regulated. This receives input signals from the sensors 28, 30, 32, 42 and 46 and controls, among other things, the actuator 26, the injector 16 and the ignition system 36 at.

The internal combustion engine 10 shown in Figure 1 is operated according to the 4-stroke principle. In this case, a valve overlap of the intake valve 20 and the exhaust valve 38 is possible. This means that in the area of top dead center between a Ausschiebetakt and an intake stroke at the same time both valves 20 and 38 can be opened. As a result, an internal exhaust gas recirculation can be realized. For the operation of the internal combustion engine 10, it is important to be able to determine as exactly as possible which air charge is located in the combustion chamber 14. For this purpose, a computer program is stored on a memory of the control and regulating device 48, which serves to control a method, which will now be explained in more detail with reference to Figures 2-6.

FIG. 2 shows how to obtain the air charge present in the combustion chamber 14 of the internal combustion engine 10 by means of a partial method A. Thereafter, the rpm nmot provided by the rpm sensor 46 and a pressure ratio fp are fed into a characteristic diagram 50. The pressure ratio fp is obtained by dividing in block 52 the pressure ps provided in the intake passage 22 by the pressure sensor 30 by an ambient pressure pu. The provision of the ambient pressure pu will be explained below in detail. The map 50 provides a value rl '. In the context of a density correction, this is multiplied in FIG. 54 by a factor fpu, which is obtained by dividing in block 56 the ambient pressure pu by the standard pressure of 1013 hPa.

Similarly, in FIG. 58, multiplication by a factor of ftb obtained in 60 by dividing a temperature Tbr by the standard temperature of 273K is performed. The temperature Tbr is the gas temperature in the combustion chamber 14 at a time when the inlet valve 20 closes. In the simplest case, the temperature Tbr is simply set equal to the temperature detected by the temperature sensor 32. Alternatively, the temperature Tbr but also taking into account a further detected temperature, such as a cooling water temperature, a Exhaust gas temperature and / or a cylinder head temperature can be obtained.

The ambient pressure pu used as input variable in FIG. 2 is not measured in the present case, but is modeled (compare FIG. 3, method B). From this it can be seen that in 62 the difference between the pressure ps detected by the pressure sensor 30 in the intake passage 22 and a modeled pressure psmod is first formed. The provision of the modeled pressure psmod will be explained in more detail below. The pressure difference dp resulting in 62 can be supplied via a first threshold value switch 64 to a first integrator 66, by means of which the ambient pressure pu is learned. The pressure difference dp can be supplied via a second threshold value switch 68 to a second integrator 70, by means of which an offset ofmsndk can be learned. The positions of the two threshold switches 64 and 68 depend on an air mass flow msdk, which flows over the throttle valve 24 and in turn from the position of

Throttle valve 24 depends. If the value msdk is less than or equal to a limit or a threshold value S, the pressure difference dp is supplied to the second integrator 70, whereas if the value msdk is greater than the threshold value S, the pressure difference dp is supplied to the first integrator 66.

FIG. 4 shows how the modeled pressure psmod required for the pressure difference dp in FIG. 3 is obtained in the intake duct 22 (method C)

Difference from an air mass rldkroh flowing into the intake duct 22 and an air mass rldk flowing from the intake duct 22 into the combustion chamber 14 are formed. The determination of the air mass rldkroh will be explained in more detail below. The value rldk is based on the already 2, where the divisor 52 is addressed instead of the detected pressure ps with the pressure psmod modeled in a temporally preceding step. The difference drl obtained in 72 is multiplied in 74 by a stroke volume Vh of the cylinder 12 and a standard density pθ. This gives the absolute value drl an absolute mass, which is summed up in 76. The result is multiplied in 78 by the gas constant R and the above-mentioned temperature Tbr and by a

Volume Vs of the intake port 22 divided. The result is a modeled pressure psmod in the intake passage 22.

It will now be explained how the value rldkroh required for addressing the difference former 72 in FIG. 4 is obtained

(compare Figure 5, method D). A map 80 is addressed on the one hand with an angle wdkba, which is detected by the throttle sensor 28. On the other hand, this map 80 is addressed with a factor rpmod, which is obtained in a divisor 82, which in turn is addressed with the modeled pressure psmod in the intake passage 22 and the ambient pressure pu. The throttle position wdkba is a measure of the opening area, and the pressure ratio rpmod is a measure of the flow rate.

The output of the map 80 is linked in FIG. 84 to the throttle position 24 offset ofmsndk determined in accordance with the method B already explained in connection with FIG. However, the initial size obtained in this way only applies to the standard density of the air. The inflow rlrohdk at the current air density is obtained by the multiplications in 86 and 88 with the factor fpu already known from FIG. 2 and a factor ftu. The latter is obtained from the root of the quotient the standard temperature of 273 K and a temperature Tvdk. The latter in turn is the temperature upstream of the throttle valve 24, which can be equated with the temperature detected by the temperature sensor 32 for simplicity.

The combination of the individual methods A-D explained in connection with FIGS. 2 to 5 is again shown overall in FIG. It can be seen that the air filling rl present in the combustion chamber 14 is ultimately only obtained with the input variables nmot (speed sensor 46), ps (pressure sensor 30), wdkba (throttle sensor 28) and Tvdk (temperature sensor 32). In this case, especially by considering the ratio between the prevailing in the intake passage 22 pressure ps and the ambient pressure pu in the process block A, a reliable determination of the air filling rl is possible even in systems with large camshaft or valve overlap.

The physical basis for this is that at one

Exhaust overlap exhaust from the exhaust pipe 40 flows back through the combustion chamber 14 into the intake passage 22. This reflux rate is dependent on the ratio between pressure in the intake passage 22 and pressure in the exhaust pipe 40, and the valve overlap time. This is taken into account by the map 50 in process block A. This is based on the assumption that the pressure in the exhaust pipe 40 can be approximated by the ambient pressure. The valve overlap time in turn depends on the speed nmot and the pressure ps.

Claims

claims

A method for operating an internal combustion engine (10), wherein an air charge (rl) in a combustion chamber (14) taking into account a pressure (ps) in an intake passage (22) is determined, characterized in that the

Air filling (rl) is determined based on a model (A), which receives as input variables a speed (nmot) of a crankshaft (44) and a ratio of the pressure (ps) in the intake passage (22) to an ambient pressure (pu).

2. The method according to claim 1, characterized in that the model (A) as an input quantity additionally receives a temperature (Tbr) of the air present in the combustion chamber (14).

3. The method according to claim 2, characterized in that it is assumed that the temperature (Tbr) of the im

Combustion chamber (14) existing air equal to a detected temperature of the air in the intake passage (22).

4. The method according to claim 2, characterized in that the temperature of the existing air in the combustion chamber is determined using a model which as

Input variables a detected temperature of the air in the intake passage and at least one further detected temperature of the internal combustion engine, in particular a Cooling water temperature, an exhaust gas temperature, and / or a cylinder head temperature receives.

5. The method according to any one of the preceding claims, characterized in that the ambient pressure (pu) is determined based on a model (B), which as

Inputs a difference (dp) between a detected (ps) and a modeled pressure (psmod) receives in the intake passage (22).

6. The method according to claim 5, characterized in that the ambient pressure (pu) is only determined when the

Throttle opening or an equivalent size (msdk) reaches and / or exceeds a threshold (S).

7. The method according to any one of claims 5 or 6, characterized in that the modeled pressure (psmod) in the intake passage (22) is determined based on a model (C), which as input a difference (drl) between a in the intake passage ( 22) incoming air mass (rldk) and one from the intake passage (22) into the combustion chamber (14) flowing air mass (rldkroh) receives.

8. The method according to claim 7, characterized in that from the intake passage (22) into the combustion chamber (14) flowing air mass (rldkroh) is determined based on a model (D), which as input a position (wdkba) of a throttle valve (24 ) receives.

9. The method according to claim 8, characterized in that the model (D) additionally receives a correction value (ofmsndk) of a throttle characteristic curve, which determines from the difference (dp) between modeled (psmod) and detected pressure (ps) in the intake passage (22) becomes.

10. The method according to claim 9, characterized in that the correction quantity (ofmsndk) is only determined if the throttle opening or an equivalent size (msdk) is less than and / or reaches a threshold (S).

11. The method according to any one of the preceding claims, that at least one model (A, D) comprises a characteristic and / or a map (50, 80).

12. Computer program, characterized in that it is programmed for use in a method according to one of the preceding claims.

13. Electrical storage medium for a control and / or regulating device (48) of an internal combustion engine (10), characterized in that a computer program for use in a method of claims 1 to 11 is stored on it.

14. Control and / or regulating device (48) for a

Internal combustion engine (10), characterized in that it is programmed for use in a method according to one of claims 1 to 11.